Tool for grinding watch crystals



I w. M. SANDEFUR. TOOL FOR GRINDING WATCH CRYSTALS.

APPLICATION FILED SEPT. 2, I920.

Patented June 6, 1922.

lull

OFFICE.

TOOL FOR GRINDING WATCH CRYSTALS.

' Specification of Letters Patent.

Patented June 6, 1922.

Application filed September 2, 1820. Serial No. 407,631.

such as will enable others skilled in the art to which it appertains tomake and use the same, reference being had to the accompanying drawings,and to the letters and figures of reference marked thereon, which form apart of this specification.

This invention, while relating generally to grinding and polishingmachines and tools, has more particular reference to a simple tool forgrinding watch crystals.

Almost all tools for this purpose on the market are rather expensive andslow in operation, since practically all are lathe attachments. Infitting crystals it is necessary to try the same in the watch bezels atshort intervals when grinding them down, since there is very littledifference between a crystal that fits and one that is a trifle toosmall. Therefore, in order to do this with lathe machines, the operatorhas to take the glass out of the lathe machine and try the same in thewatch bezel, and put it back in the lathe again, which requires time torecenter.

The object of my invention is to provide a very simple file for watchcrystals which obviates the use of a lathe, and which has the advantageof speed in use.

With this object in view, the invention resides in a tool for thepurpose described, characterized by the provision of a backplate,removably carrying clamping members for a plurality of superposedsandpaper strips disposed upon said back-plate,- and securely held bysaid clamping members in use.

The accompanying drawing clearly discloses the preferred form of myinvention, although it is to be understood that I do not desire to berestricted thereto, since changes may be made within the scope of theappended claim without departing from the spirit of the invention, ornecessarily sacrificing any of its advantages. Briefly described:

Figure 1 is a View in perspective of the tool of my invention;

Figure 2 is a fragmentary view in sideeleration thereof,

Figure 3 is a fragmentary View in bottom plan, and

Figure e is a detached detail View in perspective of one of the clampingmembers.

Referring now in detail to the drawing:

1 designates a base, or back-plate, which may be of any preferred lengthfor convenient manipulation by the operator. Said plate is provided withtwo apertures 2, 2, through each. of which projects a stem 3, carried bya clamping member l, the latter being preferably constructed as a platehaving angled terminals 5, 5, one of said terminals being adapted, inuse, to bear against the base plate 1, and the other of the terminalsagainst a plurality of superposed sand-paper sheets, or strips, 6. Thetermi nal of each stem 3 is exteriorly threaded, as shown at 7, for thereception of a wing-nut 8, which is screwed upon said threaded extremityto clamp the plate 1 against the sand-paper 6, a washer 9 beinginterposed between the nut 8 and the base pate l.

In operation, the parts are assembled as shown in Figures 1, 2 and 3-with the clamping members 4, a tightly holding the sandpaper 6 againstthe base plate 1, and the tool is used by reciprocating the same againstthe watch crystal. The sand-paper 6, used in connection with my tool, isvery line, so that the glass of the watch crystal will not be chipped,as is the result when the common steel file, used by many operators, isutilized. My tool, using fine sand-paper, also leaves the edge of thecrystal so smooth that it is not noticeable when it has been grounddown. I have found by experiment that it is advisable to use about tenstrips of sandpaper in connection with the tool, and when one strip ofpaper begins to stop cutting, the same is torn off and the user of thetool has another good surface.

I have also found, in operation, that by the use of a plurality ofsuperposed sandpaper strips, I obtain a cushioning effect which makesthe tool out much faster and more evenly.

Having thus described my invention, the many advantages thereof will beapparent, especially to those skilled in the art to which it pertains.

lVhat I claim to be new and upon which I desire to obtain Letters Patentis:

A hand bufier comprising a back plate for 10 a threaded extensionintegral with the plate and projecting through the opening in the backplate, said opening being sufficiently large to permit the positivegripping of a maximum or minimum number of abrasive strips by itscoacting bent portion, and a ing nut in threaded engagement with thethreaded extension.

In testimony whereof I hereunto a'tfix my signature.

WILLIAM MALLOVV SANDEFUR.

